Application of proton reactivity in modeling the electronic structure of reactive chemical intermediates, interpreting their resonance Raman spectra in aqueous solution, and testing theoretical procedures has been demonstrated. The case of phenoxyl radicals (p-XC6H4O.), for which there has been persistent disagreement between the structural models derived from purely spectroscopic arguments and ab initio MO calculations, is discussed. II has been shown that the neutral p-aminophenoxyl (X = NH2) radical deprotonates in basic aqueous solutions (pK(a) = 14.5), implying a highly zwitterionic structure with formal positive charge on amine nitrogen, an amide-like CN bond (less than or equal to 1.33 Angstrom), and near planarity of the molecular geometry. The radical protonates at oxygen, rather than nitrogen, the proton dissociation constant (pK(a) = 2.2) corresponding to similar to 36% negative electronic charge on the O atom and a CO bond length of similar to 1.267 Angstrom. This chemical model of the radical structure contrasts with the ab initio UNO-CAS/G-31G* (pyramidal) and ROHF/[32/2] (planar) models which predict CO/CN bond lengths of 1.237/1.395 and 1.367/1.38 Angstrom, respectively. Both ab initio structures relate to radical protonation on the nitrogen position and not the oxygen. In the proton reactivity models of para-substituted phenoxyl radicals, the CO bond length increases in the order F < H < CH3 << OCH3 similar to OH << NH2 < O-, which is quite different from the UNO-CAS/6-31G* predicted order NH2 < OH similar to Cl < H < F << O-. The near equivalence of the NH2 and O- substitutions, observed in spectroscopic and electron-transfer properties of p-aminophenoxyl (X = NH2) and p-benzosemiquinone anion (X = O-) radicals in water, is readily explainable by the structural models derived from proton reactivity but not by the calculated structures. It has been established that solvation is primarily responsible for the observed substituent effects on the spectra, structure, and chemistry of phenoxyl radicals in water.